Ishbosheth is murdered after losing the support of his general (Abner) and the rest of Israel; Abner murdered by David’s men after his defection; Michal (Saul’s daughter) returns to David: 2 Samuel 3–4
Caught in a power struggle between two powerful men, Michal seems to have been moved around to suit the politics of the day.
She was given to David, but only because Saul hoped David would be killed in the attempt to raise the price he had set. After David fled, with Michal telling her father that David had threatened to kill her if she didn’t help, Saul gave her to another Benjamite, Palti. We really can’t say whether it was part of the pragmatic politics of the day (and removing any claim David might have had to the throne), or whether it was spite, or whether it was Saul’s intention to protect his daughter from a violent man. After Saul died, and Ishbosheth started to lose support, David demanded her return and got her back.
We’re not told how Michal felt, but Palti was devastated:
2 Samuel 3:15-16 So Ishbosheth took Michal away from her husband, Palti son of Laish. Palti followed along behind her as far as Bahurim, weeping as he went. Then Abner told him, ‘Go back home!’ So Palti returned.
The text is silent on the propriety of all this. It just gives us the sequence of events. We don’t even know whether Michal’s marriage to Palti was any more or less acceptable than David’s multiple marriages.
The Bible’s sole command on this issue of multiple partners is in the ten commandments: Do not commit adultery. Kings have one more warning: do not take many wives (how many is many?). Some commentators take all this to suggest the practice of polygamy was tolerated rather than approved by God, similar to the way God tolerated divorce (see Matthew 5:27-30 and Matthew 19:1-11).
There’s also an interesting commentary on Michal at: Women of the Bible – Michal